Type I error rates of multi-arm multi-stage clinical trials: strong control and impact of intermediate outcomes

Table 1 Design of the six-arm four-stage STAMPEDE trial in prostate cancer

Stage (j)	Target	Outcome	One-sided significance	Power (ω _j)	Required control
	HR		level (α _j)		arm events
1	0.75	FFS	0.500	0.95	113
2	0.75	FFS	0.250	0.95	216
3	0.75	FFS	0.100	0.95	334
4	0.75	OS	0.025	0.90	403
Overall			0.013	0.83

ISSN: 1745-6215